The present invention relates to Nuclear Magnetic Resonance (NMR) imaging and spectroscopy and, more particularly, to novel pulse sequences for the generation of quantum coherence of other than the first order, to suppress response signal generation by the resonance of at least one undesired nuclear species present in the sample being investigated.
It is well known that, due to its relatively great natural abundance and high gyromagnetic ratio (about 42.58 MHz/T), the most readily observed species of nuclei is .sup.1 H. It is also well known that biological material contains a large amount of .sup.1 H nuclei, most of which are contained in water (H.sub.2 O) molecules. Accordingly, it is by far easier to measure the amount, and the associated constants T.sub.1 and T.sub.2, of .sup.1 H nuclei in water molecules than it is to measure the amount, and/or constants T.sub.1 and T.sub.2, of any other .sup.1 H-containing nuclear species. While it is often desirable to observe these other species, which typically yield information as to the presence and relative naturally-occurring concentration of many metabolites in areas/organs of interest, it is usually difficult to so observe these other nuclear species in practice. The modern NMR imager and/or spectrometer has the capability to be tuned to the NMR response signals radiated by the other species, but the intensity of the NMR response signal radiated by the H.sub.2 O molecules, in that same biological sample, renders the other species NMR response signal unobservable. Thus, it is highly desirable to provide a procedure by which the NMR response signal from an undesired nuclear species, such as the .sup.1 H NMR response signal from the water molecule, can be selectively eliminated to render more easily observable the NMR response signals of other species, and especially those NMR response signals of other species of the same type of nucleus.